Copolymer degradation

Bakkum FA, Trimbos JB, Dalmeyer RAJ, and van Blitterswijk CA. Preventing postoperative intraper-itoneal adhesion formation with Polyactive A degradable copolymer acting as a barrier. J Mater Sci Mater Med, 1995, 6, 41 5. 

The formation of a cyclic carbonate, e.g. propylene carbonate, accompanying the copolymerisation has been explained in terms of the backbiting reaction involving zinc alcoholate species [206,207], This has been confirmed recently [147] by degrading polypropylene carbonate) by using catalysts with zinc phenolate species. The degraded copolymer thus obtained was terminated in its chains with zinc alcoholate species and phenylcarbonate groups. The course... 

On the other hand, polypropylene carbonate) degradation rim in the presence of catalysts containing zinc alcoholate species resulted in the formation of degraded copolymer chains terminated with zinc carbonate species [scheme (31)] [147] ... 

Figure 2. Frequency distributions of polyene sequences in PVC and degraded copolymers...

Both acetic acid and acetaldehyde have an absorption in the 3100 cm-1 region of the infrared and are unlikely since no absorption in this region was observed. When the IR spectrum of homopolymer PVC impregnated with acetyl chloride was measured, two absorptions in the carbonyl region are observed at 1776 and 1722 cm"1. These two absorptions correspond quite well with those of the degraded copolymer. It does however indicate that the radical has abstracted a chlorine from the polymer, a process generally considered unlikely. 

Degradative Copolymer Formation by Friedel-Crafts Coupling... 

Fig. 9. J-R curves of the non-degraded copolymer, EPBCO, and the controlled-rheology copolymers, EPBC-CRIOI, EPBC-CR332 and EPBC-CR471.

Finally, the reactor-made copolymer, EPBCO-2, results to be a very tough material with excellent mechanical properties and above all, superior processing properties, analogous to those of peroxide-degraded copolymers. 

The ESR technique has permitted to identify initial rupture points in mechanically degraded copolymers. Lazar and Szocs [53] investigated random, block, and graft copolymers of methylmethacrylate (MMA) and styrene (S). They found in a degraded mixture of equal parts MMA and S homopolymers equal concentrations of MMA and S radicals. In a random copolymer (MMA S = 1 1) the styrene radical prevailed clearly. By comparing the reactions of mechano-radicals in ball-milled PP with those of 7-radicals Kurokawa et al. [54] concluded that the mechano-radicals were produced and trapped on the fresh surfaces created by the breaking-up of solid polypropylene. 

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